F.O.G. separator control

ABSTRACT

A separator for separating F.O.G. from an effluent that contains F.O.G. includes a tank, an inlet to the tank for receiving effluent that contains F.O.G., and an outlet to allow grey water to leave the tank. The tank has a size to enable stratification of a layer of F.O.G. present in the tank on water in the tank, and first and second thermocouples are positioned at differing levels in the tank. Conductors couple the thermocouples to sensors, and differing voltages in the thermocouples can be sensed to determine if the thermocouples are surrounded by F.O.G. or water.

This application is a division of utility application Ser. No.12/121,861 filed May 16, 2008, now U.S. Pat. No. 7,828,960, which claimsthe benefit of the filing date of provisional application 60/938,317filed May 16, 2007.

BACKGROUND OF THE INVENTION

Oil, grease and solid waste contaminant removal or recovery systems arewell known in the prior art. Over the past thirty years there has been asteady move towards requiring food handling facilities to have systemsfor servicing kitchen grease and solid waste bearing water flows. Sewersystem lines can become clogged from the fats, oil and grease wastematerials (hereinafter referred to as “F.O.G.”) put into the sewersystem from food handling facilities. This has led more and more sewerauthorities to implement fats, oils and grease control programs. Theseprograms regulate food handling facilities and the manner in which theyprocess F.O.G.s. The object of many of these programs is to ensure thatfood handling facilities remove as much of the F.O.G. as possible fromthe effluent flow, thereby releasing only grey water to the sewersystem.

Active separators remove F.O.G. from the effluent, typically by someskimming operation. Skimming when skimming is required and not skimmingwhen it is not required is an issue that has not yet been preciselyaddressed by the art. The traditional methodology is simply to use atimer that turns on the skimming apparatus at a certain time of day andruns it for a certain period, providing the user only with control as tothe time of day and duration. For installations that have very regularschedules, this may be sufficient. However, for other installations thatoperate on less than a regular schedule, problems can arise. Schedulevariations can be as simple as the differences between weekday andweekend operation. Also, for installations such as school cafeteriasthat do not operate during the summer, F.O.G. will not be added to theeffluent during the summer, so there is not a reason to run theseparator during the summer. Nonetheless, if the separator works on adaily schedule according to its timer, it will run even if there is noF.O.G. to be removed.

One of the downsides of this operation, besides the wasted energy ofskimmer operation, is that when all of the F.O.G. is removed, the waterbecomes exposed. There may be food solids remaining in the water thatare decomposing and off-gassing foul odors. If a F.O.G. mat is allowedto remain on the water, the odor is contained within the water. Also,humidity emanating from the water can rise into the electronics andprovide a challenge to the longevity of the electronics.

SUMMARY OF THE INVENTION

The present invention fulfills one or more of these needs in the art byproviding a separator for separating F.O.G. from an effluent thatcontains F.O.G. including a tank, an inlet to the tank for receivingeffluent that contains F.O.G. and an outlet to allow grey water to leavethe tank, the tank having a size to enable stratification to form alayer of F.O.G. in the tank on top of water in the tank. First andsecond thermocouples are located at differing levels in the tank, andconductors couple the thermocouples to a control box. The control boxreads differing voltages in the thermocouples to determine if thethermocouples are surrounded by F.O.G. or water.

Typically, the tank has a top and the thermocouples are mounted on rodsthat extend down from the top. The thermocouples may be mounted at lowerends of their respective rods, with the first rod being longer than thesecond rod. In some embodiments, the tank has a defined capacity forholding F.O.G. and a first rod positions a thermocouple at a level wherethe tank is considered to be 75% of the defined capacity, and a secondrod positions a thermocouple at a level where the tank is considered tobe 50% of the defined capacity.

In one embodiment the thermocouples may have conductors extending to aconnector, whereby an output box may be selectively connected to theconnector for periodic sensing to determine if the thermocouples aresurrounded by F.O.G. or water. The output box can be considered a partof the novel combination, and if so, the output box is typicallyconfigured to periodically input a current to heating elements at thethermocouples and a volt meter in the box connected to the thermocouplesmeasures the output voltages of the thermocouples.

In another embodiment the separator has a skimmer and the control systemthat acts on the sensed voltages determines when to skim. If theseparator has a skimmer, the control system may actuate the skimmer whenthe thermocouple on the first rod is surrounded by F.O.G. In a separatorthat has a skimmer, the system can be used with only one thermocoupleand a timer. The thermocouple's sensing of F.O.G. can indicate whenskimming is to commence, and the time can be used to terminate skimmingafter a pre-defined interval.

The invention can also be considered as a method including in sequencetaking a first measure of the temperature of two thermocouples in thetank, applying heat to the two thermocouples in the tank for a fixedperiod of time, taking a second measure of the temperature of twothermocouples in the tank. Differences in the first and second measuresof the temperature for the two thermocouples are then evaluated. Foreach thermocouple, if the difference in the first and second measures ofthe temperature for that thermocouple is below a threshold, the methodincludes generating a signal indicative that the thermocouple isimmersed in water in the tank. If the difference in the first and secondmeasures of the temperature for that thermocouple exceeds the threshold,the method proceeds as generating a signal indicative that thethermocouple is immersed in F.O.G.

Preferably, taking the measures comprise measuring a voltage across thethermocouple.

If the difference in the first and second measures of the temperaturefor thermocouple exceeds a second, higher threshold, the method caninclude generating a signal indicative that the thermocouple is immersedin air. Further, it can include signaling an alarm in response to asignal indicative that one of the thermocouples is immersed in air.

The method may also include operating a skimmer to skim F.O.G. fromwater in the tank in response to a signal indicative that one of thethermocouples is immersed in F.O.G. In another embodiment method mayinclude removably coupling an output box to an electrical connector onthe tank to input a current to a heater in the tank and to measureoutput voltages of the thermocouples, and evaluating differences in thefirst and second measures of the temperature for the two thermocouplesis accomplished using the output voltages at the output box. The methodcan also include terminating skimming after a predefined time interval,rather than upon sensing with a second thermocouple.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood by a reading of the DetailedDescription of the Examples of the Invention along with a review of thedrawings, in which:

FIG. 1 is a schematic view of an active F.O.G. separator equipped withan embodiment of the invention;

FIG. 2 is a schematic view of a passive separator equipped with anembodiment of the invention;

FIG. 3 is a schematic view of the embodiment of FIG. 2;

FIG. 4 is a flowchart of control operation; and

FIG. 5 is a schematic view of an electrical circuit for embodiments ofthe invention.

DETAILED DESCRIPTION OF EXAMPLES OF THE INVENTION

The preferred embodiment provides a F.O.G. separator with a controlsystem that senses a F.O.G. trap layer sensor using thermocouples. Thepreferred embodiment has two rods that are suspended from the ceiling ofa grease trap or other passive separator, such as Thermaco's Trapzilla®F.O.G. separator shown in FIGS. 2 and 3. It can also be used with activeseparators that do skimming, such as Thermaco's Big Dipper® separatorsshown in FIG. 1. As used in this application, “skimming” includes otherways of taking the F.O.G. off the top, including opening spouts thatdrain the F.O.G. (see U.S. Pat. No. 7,186,346 for examples), pumping theF.O.G. (see U.S. Pat. No. 6,517,715 for an example), or other activemethods.

Rods 12, 14 are of differing length, and each has at its end athermocouple and heater. Each thermocouple and heater has wires thattravel inside the respective rods to a control box 18 in the embodimentof FIG. 1 in the roof of the unit. The control box 18 is configured toperiodically input current to the heating element. A volt meter in thebox 18 on the output lines of the thermocouple measures the outputvoltage of the thermocouple. For the embodiments of FIGS. 2 and 3, thecontrol box can be selectively connected through the connector 17 in theroof of the unit.

The thermocouple output voltage varies with its temperature, and itstemperature response to the applied voltage varies with the dissipationof heat from the heater into the surrounding liquid. If the liquid iswater, the heat dissipation from the heater is at a faster rate than ifthe heater is located in F.O.G. so if the thermocouple is in F.O.G. itstemperature will rise faster than if it is in water. If the heater is inair, the temperature rise is much faster yet. Thus, the temperature riseof the thermocouple and, hence its output voltage, will vary dependingon whether the thermocouple is immersed in air, water or F.O.G. Thisdifference is sufficient to enable control or output box 18 to identifywhether one or more of the thermocouple probes is located in air, F.O.G.or water.

The thermocouples are useful on the active F.O.G. removal units, such asthe Big Dipper. As seen in FIG. 1, such active units include a container30 that receives effluent from an inlet 31 and allows the flow rate toslow sufficiently that a F.O.G. mat 38 can collect on top of the greywater 40. The active unit has one or more rotating disks 32 formed of aplastic or like material to which F.O.G. contaminants are attracted.Typically, the rotation of the disk is in an at least partially immersedcondition, which allows the oil 46 that floats on grey water 40 to clingto one or both sides of the disk so that contaminants are removed fromthe body of water upon rotation of the disk. Wipers 34 are typicallyused to scrape the F.O.G. from the opposite sides of the disk andchannel them to a collection or disposal storage unit. Examples of suchunits are seen in U.S. Pat. Nos. 7,208,080, 7,186,346, and 6,491,830,all commonly assigned with this application and the relevant disclosuresof which are hereby incorporated by reference.

Numerous advantages can result when the active separator is used withsensors that measure when a sufficient F.O.G. mat 38 is present in thecontainer 30 to warrant operation of the active separator, and thatavoid or terminate operation when not needed.

This type of control of the operation avoids wasted operation and itavoids operation for periods when operation is not needed. In someinstances, a particularly heavy load of F.O.G. needs removal, and if theskimmer operates for a pre-set removal period, inadequate removal may bethe result.

Also, by halting the removal of F.O.G. early enough, so as to alwaysleave a slight layer of F.O.G. on the top of the water, the escape offoul odors from the water that would be exposed by complete removal ofthe F.O.G. can be avoided. As seen in FIG. 1 detector 12 is slightlybelow the static water line 46. By terminating operation as soon as thedetector 12 senses water, rather than F.O.G., a slight F.O.G. matremains above the grey water 40. This also avoids the release ofhumidity that can challenge the longevity of electronics and other gearof the separator.

A logic circuit can be provided to indicate a malfunction has occurredrequiring service if the lower most sensor 14 continues to detect F.O.G.after separator operation for enough time that F.O.G. removal should becomplete.

In the circuitry, a rate of rise of temperature of a probe that isimmersed in F.O.G. will be greater than the rate of rise of a probe thatis immersed in water. The ratio of the rate of rise of temperature inF.O.G. to rate of rise in water may often be on the order of 2 to 1. Theratio will be relatively constant over normal operating temperatureranges.

When a sufficiently thick level of F.O.G. is sensed by the lower probe14, the electronics 18 can go through a predefined sequence. The firststep is actuation of a heater 49 which is immersed in the water (as isconventional) to raise the temperature of the liquids so as to assurethat the F.O.G. will be in a liquefied form. This can be followed byoperation of the active skimmer 32, which continues until such time asthe upper level thermocouple 12 begins to sense that it is immersed inwater, rather than F.O.G., at which time the active skimmer is stopped.The signals to operate the skimmer can be comparable to thoseconventionally received from a timer for timer-operated skimmers.

If the rate of rise of temperature for either thermocouple isextraordinarily fast, logic in the electronics 18 can sense that thethermocouple is in air, rather than in F.O.G. or water. Suitable logiccan be provided to deal with that circumstance. In particular, for aF.O.G. removal separator that is provided with an automatic solidstransfer unit (such as is shown in U.S. Pat. No. 6,491,830 or 5,360,555)the fact that the sensor is in air indicates that the automatic solidstransfer unit should not operate.

The provision of the sensors enables the elimination of the conventionalelectromechanical timer as the control of when to turn on the skimmer.If desired, a timer can be used to determine when to send sensingvoltage to the probes. Also, in some instances the collection canisterfor removed F.O.G. is of a limited capacity, so that allowing F.O.G. tobe directed to the canister from the skimmer for an unspecified periodof time risks overflowing the canister. In such cases it may bepreferable to use a timer to terminate skimming after a predefined timeinterval, although skimming starts when a thermocouple senses F.O.G. Insuch installations, only the one thermocouple is needed.

F.O.G. removal can also be obtained with more passive equipment such asa grease trap or an apparatus as described in U.S. patent applicationSer. No. 11/413,034, filed Apr. 27, 2006, published as 2007/0251879-A1,issued as U.S. Pat. No. 7,367,459 and commonly assigned with thisapplication. The relevant disclosure of U.S. Pat. No. 7,367,459 ishereby incorporated by reference. That patent describes a F.O.G. trapfor separating F.O.G. and solid waste from waste water. An example isseen in FIGS. 2 and 3 of this application. The F.O.G. trap includes atank 60 having a conically shaped bottom 62. A divider 63 divides thetank into an upper chamber and a lower chamber. A hole (not shown in theFIG. 2 or 3) near an upper part of the divider 63 allows F.O.G. to riseinto the upper chamber. An inlet invert 64 in the tank receives incomingwaste water, while an outlet invert 66 removes water from the tank. Alid 68 covers the tank. A pipe 70 extends through the lid, upperchamber, and the divider for pumping solid waste out of the lowerchamber, as well as the F.O.G.s, most grey water having passed throughthe outlet invert 66.

Two vertical rods 12 and 14 supported by lid 68 have theheater/thermocouple assemblies in their lower 1 to 2 inches. Theremainder of the column lengths of the rods is made up of conduit forcarrying the wires to the top and for supporting the heater/thermocoupleat the correct depth within the tank. The longer rod 14 preferablyterminates at the level where the tank is considered to be 75% full ofF.O.G., and the shorter one is at the 50% level. Other locations can beused. The power and thermocouple wires come from the top of the rods andconnect through connector 17 to allow for periodic connection on theoutside of the unit to the “output box” (not shown). The output box,described below, is in the possession of a sewer official or otherperson assessing the condition of the unit. The wiring from the rods tothe connector 17 is preferably sufficiently long to allow the lid 68, tobe removed and for the addition of expansion collars. The preferredthermocouple is available from Watlow Electric Manufacturing Company,12001 Lackland Road, St. Louis, Mo., USA 63146 as their Firerod Internalthermocouple, Style A.

FIG. 4 is a flow chart for the process which will determine if the tipsof the probes are in water or oil (i.e. greater or lower heater andthermocouple temperature and therefore greater or lower thermocouplevoltage). This flow chart can be carried out with various electricalcircuits for the “output box” that the sewer official will carry to theF.O.G. separator to assess its condition. The logical flow can also beused in control box 18 to generate control signals for operation of thesystem of FIG. 1.

In the process, the voltages of the two thermocouples are measured atstage A and again at stage B, with power being supplied to the heatersbetween A and B. The changes in the voltages of the thermocouples arecomputed at stage C. If the voltage change exceeds a threshold(i.e. >x.xx mV), then an indication that the rate of rise was fast canbe generated, such as by a lighting a red LED (stage D) or by supplyinga “thermocouple is in F.O.G.” signal to a controller. A voltage changebelow the threshold indicates that the thermocouple is in water and agreen LED can be lit or a thermocouple is in water” signal can be sentto the controller. If the voltage is over a higher threshold, similarlogic can indicate that the thermocouple is in air. The threshold, ofcourse, is determined for each separator design based upon geometry andthe length of time the heaters stay on and the time between voltagereadings. Applicants have used heaters of 50 and 200 watts and timeintervals of ten seconds, but a wide range of other values would besuitable. Time intervals measured on the order of milliseconds can beused.

FIG. 5 is a schematic for such an output box, showing components thatcould be used in the output box—several switches, additional lights,relays, batteries, charging capability, etc. Those of ordinary skill inthe art can construct such electronics or others that yield comparableresults.

In use, the sewer official would take an output box with a chargedbattery to the site where the separator is installed. He/she connects acable from the output box to the connector 17 of the separator. He/sheturns the power on the box at 100, gets a power light (then possibly aready light), presses a test push button 120, and after about 15-20seconds gets the red/green status lights 130. This accomplishes oneheating and measurement cycle (for the two probes) and is all that isrequired. He/she can tell from the combination of lights whether theseparator needs to be pumped out or not according to this logic diagram:

50% full Sensor 12 Senses F.O.G. Senses F.O.G. Senses Water 75% fullsensor 14 Senses Water Senses F.O.G. Senses Water Action for FIG. 2-3Pumping Pumping No Pumping Recommended Immediately Needed

The counterpart logic for the active separator of FIG. 1 may be:

Sensor 12 Senses F.O.G. Senses F.O.G. Senses Water Sensor 14 SensesWater Senses F.O.G. Senses Water Action No skimming Skim No Skimmingneeded Needed

In both embodiments, if the temperature rise indicates that athermocouple is in air, pumping or skimming is inappropriate. If bothare in air, a repair may be needed.

Certain modifications and improvements will occur to those skilled inthe art upon reading the foregoing description. For example, thepositioning of the thermocouple and heater in the separator can beaccomplished by means other than separate rods; the two sensors couldboth be positioned space along a single rod or they can be mounted toother items at appropriate locations within the tank. It should beunderstood that all such modifications and improvements have beenomitted for the sake of conciseness and readability, but are properlywithin the scope of the following claims.

1. In a separator tank for separating F.O.G. from an effluent thatcontains F.O.G. in which the tank has a size to enable stratification ofa layer of F.O.G. present in the tank on water in the tank, the methodcomprising in sequence: taking a first measure of the temperature of twothermocouples in the tank, applying heat to the two thermocouples in thetank for a fixed period of time, taking a second measure of thetemperature of two thermocouples in the tank, evaluating differences inthe first and second measures of the temperature for the twothermocouples, and for each thermocouple, if the difference in the firstand second measures of the temperature for that thermocouple is below athreshold, generating a signal indicative that the thermocouple isimmersed in water in the tank; and if the difference in the first andsecond measures of the temperature for that thermocouple exceeds thethreshold, generating a signal indicative that the thermocouple isimmersed in F.O.G.
 2. A method as claimed in claim 1 wherein generatingthe signal indicative that the thermocouple is immersed in F.O.G.further comprises sending a maximum F.O.G. accumulation alarm.
 3. Amethod as claimed in claim 2 wherein sending a maximum F.O.Gaccumulation alarm further comprises sending the maximum F.O.G.accumulation alarm to a remote indicator.
 4. A method as claimed inclaim 1 wherein taking the measures comprise measuring a voltage acrossthe thermocouple.
 5. A method as claimed in claim 1 wherein if thedifference in the first and second measures of the temperature for thatthermocouple exceeds a second threshold that is higher than thethreshold mentioned in claim 3, generating a signal indicative that thethermocouple is immersed in air.
 6. A method as claimed in claim 5further comprising signaling an alarm in response to a signal indicativethat one of the thermocouples is immersed in air.
 7. A method as claimedin claim 1 further comprising operating a skimmer to skim F.O.G. fromwater in the tank in response to a signal indicative that both of thethermocouples are immersed in F.O.G.
 8. A method as claimed in claim 1further comprising directing the flow of effluent from the tank basedupon the signal generated.
 9. A method as claimed in claim 1 furthercomprising removably coupling an output box to an electrical connectoron the tank to input a current to a heater in the tank and to measureoutput voltages of the thermocouples, and wherein evaluating differencesin the first and second measures of the temperature for the twothermocouples is accomplished using the output voltages at the outputbox.
 10. In a separator tank for separating F.O.G. from an effluent thatcontains F.O.G. in which the tank has a size to enable stratification ofa layer of F.O.G. present in the tank on water in the tank, the methodcomprising in sequence: taking a first measure of the temperature of atleast one thermocouple in the tank, applying heat to the at least onethermocouple in the tank for a fixed period of time, taking a secondmeasure of the temperature of the at least one thermocouple in the tank,evaluating differences in the first and second measures of thetemperature for the at least one thermocouple, and if the difference inthe first and second measures of the temperature for the at least onethermocouple is below a first threshold, generating a signal indicativethat the at least one thermocouple is immersed in water in the tank; andif the difference in the first and second measures of the temperaturefor the at least one thermocouple exceeds the first threshold,generating a signal indicative that the at least one thermocouple isimmersed in F.O.G.
 11. A method as claimed in claim 10 wherein if thedifference in the first and second measures of the temperature for theat least one thermocouple exceeds a second threshold that is higher thansaid first threshold, generating a signal indicative that the at leastone thermocouple is immersed in air.
 12. A method as claimed in claim10, wherein generating the signal indicative that the thermocouple isimmersed in F.O.G. further comprises sending a maximum F.O.G.accumulation alarm.
 13. A method as claimed in claim 12, wherein sendinga maximum F.O.G accumulation alarm further comprises, sending themaximum F.O.G. accumulation alarm to a remote indicator.
 14. A method asclaimed in claim 10, further comprising directing the flow of effluentfrom the tank based upon the signal generated.
 15. A method as claimedin claim 10, further comprising removably coupling an output box to anelectrical connector on the tank to input a current to a heater in thetank and to measure output voltages of the at least one thermocouple,and wherein evaluating differences in the first and second measures ofthe temperature for the at least one thermocouple is accomplished usingthe output voltages at the output box.
 16. In a separator tank forseparating F.O.G. from an effluent that contains F.O.G. in which thetank has a size to enable stratification of a layer of F.O.G. present inthe tank on water in the tank, the method comprising in sequence: takinga first measure of the temperature of two thermocouples in the tank,applying heat to the two thermocouples in the tank for a fixed period oftime, taking a second measure of the temperature of the twothermocouples in the tank, evaluating differences in the first andsecond measures of the temperature for the two thermocouples, for eachthermocouple, if the difference in the first and second measures of thetemperature for that thermocouple is below a threshold, generating asignal indicative that the thermocouple is immersed in water in thetank; and if the difference in the first and second measures of thetemperature for that thermocouple exceeds the threshold, generating asignal indicative that the thermocouple is immersed in F.O.G., sensingthe signal in a control box to determine if the thermocouples aresurrounded by F.O.G. or water, and if at least one of the thermocouplesis determined to be in F.O.G., operating a skimmer to remove F.O.G. 17.A method as claimed in claim 16, wherein sensing the signal in a controlbox determines if the thermocouples are surrounded by air, F.O.G. orwater.